4.13.5.9 ICE Access Prevention
The DBGU allows blockage of access to the system through the Arm
processor's ICE interface. This feature is implemented via the Force NTRST register
(DBGU_FNR), that allows assertion of the NTRST signal of the ICE interface. Writing the bit
FNTRST (Force NTRST) to 1 in this register prevents any activity on the TAP
controller.
Note:
- During ROM code execution, this bit is set (JTAG access is disabled).
- This bit has no more effect once the JTAG access is disabled in the OTPC.